To Surf a Hundred Million Stars

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!

Forget I asked, because after you click on this link, your day will be gone. Poof! Vanished, since you will find yourself buried in a magnificent, massive of the center of the Milky Way galaxy.

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And when I say massive, I mean it’s friggin’ HUGE: 24,000 x 14,000 pixels! That’s a total of a staggering 330 million pixels. It’s a combination of three images (one each in red, green, and blue to produce a true-color final product), so it’s actually—and I can’t believe I’m typing this—the combination of a billion pixels of information.

Did I mention it’s zoomable and scannable? No? Well, there goes your day.

The image, taken by my friend Stéphane Guisard at the ESO's Paranal Observatory in Chile, spans an area of the sky roughly 30° x 20°, or about twice the area of the sky you can cover up with your outstretched hand. That’s a lot of territory. Taken as part of the GigaGalaxy Zoom project, it's a mosaic of 52 fields shot over 29 nights for a total of 200 hours of exposure over 1200 separate photos.

The sheer number of stars in this image is crushing my mind. When you look at the picture above (which is only a part I cropped out from the full-size shot), you can see a whitish glow. Those are stars. Individual stars, millions of them, too small to see at the scale show, but adding together to make that glow.

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Here, let me show you. Inset here is a small piece of the image above, showing some of the background stellar glow and some of the dark clouds—huge regions of space filled with dust, which blocks the light from stars behind it. The white box outlined in the picture here looks like it's mostly just filled with white haze, right? Well, let’s blow that piece up a bit and see what’s what:

To coin a phrase: “My God, it’s full of stars!”

Look at all of them! And then compare the size of this small piece of the picture to the whole thing…and realize this is only a tiny fraction of the stars in the galaxy. There are tens of millions of stars in the whole zoomable picture at least, but hundreds of billions in the Milky Way. In other words, this huge picture crammed full of stars shows less then a thousandth of all the stars in our galaxy!